KR20190053837A - Phase Polarization Multi-Degree of Freedom Modulation Quantum Key Distribution Network Systems and Methods - Google Patents

Abstract

The present invention relates to a phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and method, comprising an Alice transmission end, a wavelength division multiplexing (WDM) Wherein the Alice stage comprises a multi-wavelength laser generator, an attenuator, a first polarization beam splitter, a first beam combiner, a phase modulator, first and second polarization controllers, Wherein the wavelength division multiplexing unit comprises a wavelength selection device, the multi-user Bob stage comprising several unit Bob client stages for receiving different frequency bands, wherein each of the unit Bob client stages comprises a second, Third and fourth polarization beam splitters, second and third beam combiners, and first through fourth photon detectors. The QKD network system used in the present invention is capable of realizing one-to-many quantum key sharing, effectively expanding the information transmission capacity, applying the phase-polarized multi-degree of freedom modulation QKD scheme and other QKD schemes.

Description

Phase Polarization Multi-Degree of Freedom Modulation Quantum Key Distribution Network Systems and Methods

FIELD OF THE INVENTION The present invention relates to the field of quantum secure communications and optical fiber communications in the field of communications, and more specifically to a phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and key distribution method.

At present, the modulation of a quantum signal generally uses a single degree of freedom modulation such as polarization, phase, frequency, and intensity. The polarization modulation of an optical signal indicates that information is loaded by adjusting the polarization direction of light. Usually, the polarization state of the optical signal is encoded by using the polarization state of two lines of the photon. Birefringence, and polarization mode dispersion, and other methods that can generally proceed with polarization compensation or stabilize polarization in order to interfere with the environment. Phase modulation refers to the encoding of information using the phase of light. The phase modulation of quantum communication is based on a Mach-Zehnder interferometer, and its key component is a phase modulator. The first proposed phase modulation scheme is based on a single equal arm MZ interferometer. Due to the influence of the environment, the length of the two arms is not stable, so that the phase difference also drifts and the interference effect is severely affected. In particular, MZ interference systems have been proposed, in which the temporal disturbance of the overlapping portions of the optical fiber has the same effect on the two pulses and the stability of the interference is greatly improved. However, even with the use of the two-arm MZ interferometer, a slight change in the arm length causes a decrease in the interference contrast .

The M-Z interferometer QKD system generally uses the BB84 protocol, the B92 protocol, and the safety of the system is based on the fact that Eve does not know the exact base used by the legitimate communication parties to encode and detect information. On the other hand, systems using the BB84 protocol and the B92 protocol must not compare the encoding base with the measurement base at the time of key formation, and thus the efficiency of the protocol is not high and the coding rate is low, so the actual application demand can not be satisfied. Differential phase encoding follows the phase encoding scheme and has a fast encoding speed, strong interference resistance capability, and an extremely long transmission distance, which is suitable for realization in a fiber optic line and can significantly improve code generation efficiency. The differential phase encoding carries information using two pulse differences between the front and back sides and improves the stability of the system because the pulses pass through the same phase and polarization change in the optical fiber and are not sensitive to various kinds of interference among the optical fibers.

A quantum key distribution method of a new phase-modulated polarization encoding has been proposed in Zhilie Tang et al., "Phase-Modulated Polarized Quantum Ciphers and Decoders and Their Applications", 2006, although it has high stability, Both the cipher and the decoder have a low utilization rate for secure communication photons. In December 2014, Jindong Wang et al., "Four state quantum ciphers and decoders and quantum key distribution system with phase-modulated polarization encoding", modulated the phase of polarized light of a line through a phase modulator, And ultimately realizes polarization encoding, which also uses a single degree of freedom of polarized light as an information carrier and proceeds with the quantum transmission. However, the orbital angular momentum can realize the encoding of high dimensional quantum information because it has multiple degrees of freedom, but orbital angular momentum multiple degree of freedom modulation is mainly applied to quantum free space communication and typical multi-channel high speed communication.

On the basis of the above-described state of the art, there has been developed a kind of phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system to realize one-to-many communication, and each user is relatively independent, It is necessary to realize safe, stable and highly efficient transmission of the quantum key distribution network system by ensuring that it is not reduced and stabilized as the number of users increases.

SUMMARY OF THE INVENTION The present invention provides a kind of phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and method to overcome the shortcomings of the prior art. This phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and method employs multi-wavelength pulses generated through a single light source multi-wavelength laser device as a carrier of multi- And each user is independent. Therefore, as the number of users increases, the speed of key generation of individual users is not reduced as the number of users increases. Therefore, the quantum key distribution network system can be safely, reliably, As shown in Fig. In addition, since the multi-user quantum key distribution network system of the phase deflection multi-degree of freedom modulation has a new quantum information encoding scheme, i.e., a differential phase encoding scheme and a polarization encoding scheme, the error rate due to unstable external environment is effectively reduced. And improves the photon utilization from the original 0.5 to 2 by improving the existing differential phase and polarization encoding combination to improve the quantum key generation rate and reduce the communication time slot latency each time.

This system uses multiwavelength laser device, attenuator, polarized beam splitter, beam combiner, phase modulator and polarization controller of a single light source as a carrier for multi-user information transmission. The phase difference between front and back pulse passing through both arms And simultaneously loads one information bit having a different pulse polarization state, and transmits each wavelength pulse through a wavelength division multiplexing unit for each legitimate user to perform corresponding polarization demodulation and phase demodulation, Each user is relatively independent, ensuring that the key generation rate of a single user is stable.

To achieve the above object, the present invention uses the following technical solutions.

A phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system comprising an Alice control stage, a wavelength division multiplexing unit and a multi-user Bob stage, wherein the Alice stage is connected to the multi-user Bob stage via a wavelength division multiplexing unit.

The Alice stage includes a multi-wavelength laser generator, an attenuator, a first polarization beam splitter, a first beam combiner, a phase modulator, a first polarization controller, and a second polarization controller.

The wavelength division multiplexing unit includes a wavelength selection device.

Wherein the multi-user Bob stage comprises a plurality of unit Bob client stages for receiving different wavelengths, wherein each unit Bob client stage comprises a second polarization beam splitter, a third polarization controller, a fourth polarization controller, a third polarization beam splitter, 4 polarization beam splitter, a second beam combiner, a third beam combiner, a first photon detector, a second photon detector, a third photon detector, and a fourth photon detector.

The multi-wavelength laser generator generates a pulse train having a plurality of wavelengths, and attenuates to a single photon pulse after passing through the attenuator. The single photon pulse is separated into vertical and horizontal polarized pulses by passing through the first polarized beam splitter , The vertical polarization and the horizontal polarization pulse are respectively passed through the upper arm path and the lower arm path and combined by the first beam combiner, and then the pulse is randomly transmitted through the phase modulator with a k? (K = 0, 1) phase Modulated, and arrives at the first polarization controller and the second polarization controller, respectively, to proceed with pulse polarization rotation. Finally, both pulses enter the Bob side in the same polarization state.

When a multi-wavelength laser pulse of the same polarization is transmitted to the wavelength router apparatus, the unit Bob client terminal of the corresponding wavelength is selected by an addressing method according to wavelength, and when passing through the second polarizing beam splitter of the unit Bob client terminal Proceeding with polarization demodulation, if a polarization bit is " 0 ", select a horizontal polarization pulse to pass through the third polarization controller; When the polarized bit is " 1 ", a vertical polarization pulse is selected to pass through the fourth polarization controller.

And the second polarized beam splitter passes through the third polarized beam splitter to form an upper arm path and a lower arm path bifurcated path, wherein the upper arm path passes through the second beam comb And the lower arm path has a rear pulse arriving at the second beam combiner and the two arms of the upper arm path and the lower arm path are interfered by the second beam combiner, The first photon detector and the second photon detector identify and respond based on the phase difference modulated by the second photon detector.

After the fourth polarization controller outputs the fourth polarization beam splitter, the upper arm path and the lower arm path are formed by passing through the fourth polarization beam splitter, wherein the upper arm path passes through the third beam comb- And the lower arm path is the arrival of the back pulse directly to the third beam combiner, where the two arms of the upper arm path and the lower arm path are interfered by the third beam combiner , The third photon detector and the fourth photon detector identify and respond based on the randomly modulated phase difference.

Preferably, the upper arm path has one T more time delay than the lower arm path.

편광 회전하고, 상기 제2 편광 조절기가 펄스를

편광 회전하되, 그중 n의 값이 각기 "0"" 또는 "1"이다. Preferably, the first polarization controller outputs a pulse

Polarized light, and the second polarization controller pulses

Polarized light, and the value of n is "0" or "1", respectively.

Preferably, the wavelength router device is a wavelength division multiplexer, an arrayed waveguide grating, a Bragg grating or a wavelength selective switch.

Preferably, the multi-wavelength laser generator comprises a multi-wavelength pulse laser device and a wavelength selector, wherein the multi-wavelength pulse laser device generates an interfering multi-wavelength pulse laser that meets the multi-unit Bob client- The selection is performed through the wavelength selection device so that the Bob client end of each unit can select a pulse laser of a corresponding wavelength.

Preferably, the wavelength selector selects a wavelength using a second-order equalization frequency interval method.

Preferably, if the first photon detector, the second photon detector, the third photon detector and the fourth photon detector respond based on the phase difference of the pulses, if the phase difference of two consecutive pulses is zero, The measurement result is " 0 ", the second detector responds, and the measurement result is " 01 "; If the phase difference of two consecutive pulses is π, the third detector responds, the measurement result is "10", the fourth detector responds, and the measurement result is "11".

Preferably, the unit Bob client end is Bobn, wherein n is a non-zero natural number.

A method of applying such a phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system includes the following procedure.

S1. Hardware Initialization: Check the software and hardware facilities of the Alice stage and each unit Bob client stage, and confirm whether the equipment is operating normally, the correct operating voltage and the appropriate operating temperature.

S2. System noise measurement: The system noise level is measured under the condition that the laser pulse string is not emitted from the Alice stage, that is, when the pulse string value is zero.

S3. Fiber Length Measurement and Pulse Time Delay Setup: A set of pulses is sent at the Alice stage, the length of the optical fibers in the link is determined by measuring the arrival time of the pulses at each Bob client end, The optical fiber length of each unit Bob client terminal is set in advance based on the length relationship between the stage and the Alice stage, and the time delay between the upper arm path and the lower arm path of each unit Bob client end is set.

S4: Wavelength addressing: The wavelength selector selects wavelength pulses suitable for use by each unit Bob client end according to the wavelength distribution scheme, assigning pulse light beams of different wavelengths to the corresponding unit Bob client end, Communication proceeds.

S5.Key Transmission: The multi-wavelength pulse generator generates a pulse whose pulse period is greater than the time delay T, attenuated to a single photon level after passing through the attenuator, and then transmitted through the first polarization beam splitter, Path and the lower arm path to form two pulses with a time delay of T. After reaching the first beam combiner, the pulses are combined and then the phase modulator, the first polarization modulator and the second polarization modulator are sequentially passed , They are transmitted in the same polarization state, and finally, each unit Bob client terminal passes through the polarization demodulation and phase demodulation.

S6. Key Filtering and Coding: Each unit Bob client side records the detector response. And wherein the first photon detectors, the second photon detectors, the third photon detectors, and the fourth photon detectors respond to the first photon detectors, the second photon detectors, the third photon detectors, and the fourth photon detectors The Alice terminal forwards the response time to the Alice terminal, and the Alice terminal forwards the corresponding key string based on the data transmitted from each unit Bob client terminal, and discards the other key string.

Preferably, each unit Bob shares the key between the client and the client.

If the security key priority is Bobi> Bobj, Bobj shares Bobi's key, Alice is the intermediate node, first encrypts Alice's and Bobi's keys using Alice's and Bobj's keys, Bobj sends the key to Bobj, decrypts it, gets Bobi's key, and shares the key with Bobi.

Each unit Bob's client-to-server key sharing is exclusive. The key of any one unit Bob client can only be shared with one unit Bob client unit, and can not be shared with another unit Bob client unit after sharing.

The effects of the present invention are as follows.

1. The phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and the key distribution method used in the present invention can realize one-to-many quantum key sharing, effectively expand the information transmission capacity, QKD scheme and other QKD schemes.

2. The present invention utilizes a phase and polarization unified modulation method that transmits 2 bits of information to one photon to improve the photon utilization from 0.5 to 2 originally, Simplify the structure, and improve the continuity, validity and key generation rate of information.

3. The present invention uses 4 electron detectors to measure atmospheric in 8 timeslots each time of communication, which means that the error rate due to the dark count of the detector when compared to the atmospheric measurement in 12 timeslots in each communication of the existing scheme 33.3%, the system is more efficient and stable. The present invention utilizes a typical DPS quantum key distribution scheme in which each phase difference is in one phase encoding through the phase difference of the bifurcated interference pulse with an encoding interval of T (i.e., time delay T and T is picosecond) And sequence attacks, effectively reducing the efficiency of the eavesdropper Eve.

1 is a structural block diagram of a wavelength division multiplexing unit and a multi-user Bob stage according to the present invention.
2 is a block diagram of a phase modulation and polarization modulation structure on the side of the ce ce according to the present invention.
3 is a block diagram of the Bob side polarization demodulation and phase demodulation structure according to the present invention.
4 is a functional block diagram of the present invention.
5 is a flowchart of the operation of the present invention.

The drawings are used to illustrate the embodiments and are not to be construed as limiting the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention.

The present invention is a point-to-multipoint networking scheme, particularly scalable to multipoint to multipoint. The described embodiments are merely one example of one-to-many approaches of the present invention, which can be extended to various other applications, such as a typical wavelength division quantum key distribution network as illustrated in FIG.

As shown in FIGS. 1 to 4, a kind of phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system includes an Alice control side, a wavelength division multiplexing unit and a multi- user Bob stage, And is connected to the multi-user Bob stage through the multiplexing unit.

The Alice stage includes a multi-wavelength laser generator 201, an attenuator 202, a first polarization beam splitter 203, a first beam combiner 204, a phase modulator 205, a first polarization controller 206 and a second polarization controller 207.

The wavelength division multiplexing unit includes a wavelength selection device.

The multi-user Bob stage includes several unit Bob client stages that receive different frequency bands. Each unit Bob client stage includes a second polarization beam splitter 301, a third polarization controller 302, a fourth polarization controller 307, Beam splitter 303, a fourth polarization beam splitter 308, a second beam combiner 304, a third beam combiner 309, a first photon detector 305, a second photon detector 306, a third photon detector 310 and a fourth photon detector 311 .

The operation of this system is as follows.

The multi-wavelength laser generator generates a pulse train having a plurality of wavelengths and then attenuates to a single photon pulse after passing through the attenuator 202. The single photon pulse passes through the first polarizing beam splitter 203 to generate vertical and horizontal polarized pulses The vertical and horizontal polarized pulses pass through the upper arm path and the lower arm path, respectively, and enter the first beam combiner 204, and then, after passing through the phase modulator 205, k = 0, 1) phase and proceeds to the first polarization controller 206 and the second polarization controller 207 to proceed with the pulse polarization rotation. Finally, both pulses enter the Bob side in the same polarization state.

When a multi-wavelength laser pulse of the same polarization is transmitted to the wavelength router apparatus 102, the unit Bob client terminal of the corresponding wavelength is selected by the addressing method according to the wavelength, and the second polarization beam splitter 301 of the unit Bob client terminal , The polarization demodulation is performed so that when the polarized bit is " 0 ", the horizontal polarization pulse is selected to pass through the third polarization controller 302; When the polarized bit is " 1 ", the vertical polarization pulse is selected to pass through the fourth polarization controller 307. [

After output from the third polarization controller, the third polarized beam splitter 303 passes through the upper arm path and the lower arm path to form a bifurcated path, in which the upper arm path passes through the second beam comb- The upper arm path and the lower arm path are bifurcated at the second beam combiner 304 and the upper arm path and the lower arm path are interfered at the second beam combiner 304. [ Next, the first photon detector 305 and the second photon detector 306 identify and respond based on the randomly modulated phase difference.

After being output from the fourth polarization controller 307, the fourth polarization beam splitter 308 is passed to form an upper arm path and a lower arm path. In the upper arm path, a front pulse passes through the third beam com And the lower arm path arrives at the third beam combiner 309. The bifurcated beams of the upper arm path and the lower arm path are transmitted to the third beam combiner 309 After the interference occurs, the third photon detector 310 and the fourth photon detector 311 identify and respond based on the randomly modulated phase difference.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

The present invention is a point-to-multipoint networking approach, particularly scalable to multipoint to multipoint. The following embodiments are merely one example of the one-to-many method of the present invention, which can be extended to various other applications, such as a typical wavelength division quantum key distribution network as shown in FIG.

In FIG. 1, the Alice stage has one multi-wavelength light source at the originating side of the pulse signal, and can generate pulse signals of different frequency bands in which several unit Bob client terminals can simultaneously communicate. Each unit Bob client terminal can receive a signal of any wavelength and it has wide applicability to the pulse wavelength, i.e. the pulse wavelength has wide applicability. In other words, after coordinating the distribution of signal wavelengths between each unit Bob client in the wavelength planning process, each unit Bob client end can still function normally. In FIG. 1, the public optical fiber 101 can be jointly used by each user, the optical fibers 103, 104 and 105 are dedicated optical fibers for each user, and the sum of the dedicated optical fiber and the common optical fiber 101 of each user is defined as the distance of each user. The wavelength router device 102 controls the path selection of each wavelength pulse signal between the control side Alice and the user side Bob.

Figure 2 is an illustration of an Alice example embodiment of a phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and method in accordance with the present invention in which the Alice stage of the system proceeds with phase modulation and polarization modulation .

The specific modulation process is as follows.

인 45°펌프광이 단일 광자 펄스

로 감쇄되는데, 그중

는 가우스형 펄스이다. 당해 단일 광자 펄스는 제1 편광 빔 스플리터203를 경과한 후 두 갈래 펄스로 분리되고, 두 갈래 펄스는 시간지연 T가 있는데, 시간지연이 T인 두 갈래 펄스가 위상 변조기PM(

,k 값이 "0"또는 "1")를 통과한 후, 펄스 형식은 각기

,

로 변화하고, 제1 편광 조절기（PC1）206은 시간지연 펄스에 대해

,

편광 회전하는데, 이때 펄스는

이며; 제2 편광 조절기（PC2）207은 단락펄스에 대하여

편광 회전을 진행하는데, 이때 펄스는

이고,

의 값은 "0"또는 "1"이다. When the polarization state is

45 [deg.] Pump is a single photon pulse

, Where

Is a Gaussian pulse. The single photon pulse is separated into two bifurcated pulses after passing through the first polarization beam splitter 203, and the bifurcated pulses have a time delay T. A bifurcated pulse with a time delay T is output from the phase modulator PM

, k value is " 0 " or " 1 "),

,

, And the first polarization controller (PC1) 206 changes to a time delay pulse

,

Polarization rotates, where the pulse is

; The second polarization controller (PC2) 207 generates a short pulse

The polarization rotation is proceeding,

ego,

Quot; 0 " or " 1 ".

의 펄스열을 발생하는데, 그중 산생된 멀티 파장 펄스는 편광이 45°이고, 펄스 주기는 시간지연 T보다 큰데, 감쇄기202를 경과하여 단일 광자 펄스로 감쇄되고; 단일 광자 펄스는 제1 편광 빔 스플리터203을 경과하여 수평편광과 수직편광의 펄스로 분리된 후 각기 상부 암 경로 및 하부 암 경로에 진입하게 되는데, 그중 상부 암 경로는 하부 암 경로보다 시간지연 T를 경과하게 되며, 그 다음 두 펄스는 위상 변조기205를 통과하게 되고, 위상 변조기205는 두 펄스에 랜덤으로 kπ의 위상（k 값이 0 또는 1）을 변조한다. 두 펄스가 동시에 제1 편광 조절기206 및 제2 편광 조절기207（다시 말하여, 편광조절기 간의 간격이 시간지연 T가 있을 경우）에 도착할 경우, 제1 편광 조절기206은 펄스를

편광 회전하고, 제2 편광 조절기207은 펄스를

편광 회전하는데, 그중 n의 값은 각기 "0" 또는 "1"이다. 이때, 두 펄스는 같은 편광상태로 광섬유를 경과하여 다중 사용자 Bob 단에 전송 진입된다. The multi-wavelength laser device 201 is a multi-

Wherein the generated multi-wavelength pulse has a polarization of 45 degrees and the pulse period is greater than the time delay T, which is attenuated to a single photon pulse by passing through the attenuator 202; The single photon pulse passes through the first polarization beam splitter 203 and is split into pulses of horizontally polarized light and vertically polarized light, and then each enters the upper arm path and the lower arm path. Among them, the upper arm path has a time delay T The next two pulses pass through a phase modulator 205 and the phase modulator 205 randomly modulates the phase (k value 0 or 1) of k [pi] to both pulses. When the two pulses arrive at the same time with the first polarization controller 206 and the second polarization controller 207 (i.e., the interval between the polarization controllers is time delay T), the first polarization controller 206 outputs a pulse

Polarized light and the second polarization controller 207 rotates the pulse

And the value of n is "0" or "1", respectively. At this time, the two pulses pass through the optical fiber in the same polarization state and are transmitted to the multi-user Bob stage.

3 is an explanatory diagram of a Bob side embodiment of a phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and method according to the present invention in which Bob1 is subjected to polarization demodulation and phase demodulation on Bob1 side, The following is a specific demodulation process.

,

로 변화하는데. 이때 수직편광은 시간지연 T를 거쳐

로 변하고, 펄스

는

와 합친다. When n = 0, the two pulse lights pass through the third polarization controller PC3, and the pulse format is

,

. At this time, the vertical polarization passes through the time delay T

, And the pulse

The

.

At that moment, the first photon detector D1 responds, at which time the corresponding key is " 00 ".

At that moment, the second photon detector D2 responds, at which time the corresponding key is " 01 ".

Likewise, when n = 1, if the third photon detector D3 responds, the corresponding key is " 10 ", and if the fourth photon detector responds, the corresponding key is " 11 ".

편광 회전하여 수직편광으로 변화하는데, 수직편광 펄스가 제3 편광 빔 스플리터303를 경과하여 반사되고, 시간지연 T를 경과하여 제2 빔 컴바이너304에 진입한다. 수평 편광펄스는 제3 편광 빔 스플리터303을 경과한 후 바로 투과하여 제2 빔 컴바이너304에 진입한다. 제4 편광 조절기307은 느린축 펄스만

편광 회전하여 수평편광으로 변화하는데,수평 편광 펄스는 제4 편광 빔 스플리터308을 경과한 후 바로 투과하여 제3 빔 컴바이너309에 진입한다. 수직 편광펄스는 제4 편광 빔 스플리터308을 경과하여 반사되고, 시간지연 T를 거쳐 제3 빔 컴바이너309에 진입한다. 제2 빔 컴바이너304에서 만난 두 펄스광은 간섭이 발생하는데, 랜덤으로 변조된 위상차 0 또는 π에 근거하여, 제1 광자 탐지기305 또는 제2 광자 탐지기306이 응답한다. 같은 이치로, 제3 빔 컴바이너309에서 만난 두 펄스광에 간섭이 발생하여, 랜덤으로 변조된 위상차 0 또는 π에 근거하여, 제3 광자 탐지기310 또는 제4 탐지기311이 응답한다. When n is " 0 ", two pulses having a time interval of T pass through the second polarization beam splitter 301 in the horizontal polarization state and enter the third polarization controller 302; When n is " 1 ", two pulses having a time interval T pass through the second polarization beam splitter 301 in the vertical polarization state and enter the polarization controller 307. [ The third polarization controller 302 receives only the fast axis pulse

Polarized light is changed to vertical polarized light, the vertical polarized light pulse is reflected after passing through the third polarization beam splitter 303, and enters the second beam combiner 304 after a time delay T elapses. The horizontal polarization pulse passes through the third polarization beam splitter 303 immediately before entering the second beam combiner 304. The fourth polarization controller 307 controls only the slow axis pulse

The polarized light is changed to horizontally polarized light, and the horizontal polarized light passes through the fourth polarization beam splitter 308 immediately before entering the third beam combiner 309. The vertical polarization pulse is reflected after passing through the fourth polarization beam splitter 308, and enters the third beam combiner 309 through the time delay T. [ The two pulse lights encountered at the second beam combiner 304 are interfered, and the first photon detector 305 or the second photon detector 306 responds based on the randomly modulated phase difference 0 or?. Likewise, interference occurs in the two pulse beams encountered at the third beam combiner 309, and the third photon detector 310 or the fourth detector 311 responds based on the randomly modulated phase difference 0 or?.

Figure 4 is a block diagram of an operational principle according to a phase polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and method, comprising an Alice control stage, a wavelength division multiplexing unit and a multi- user Bob stage, It connects to the multi-user Bob stage through the unit. Among them, the Alice stage performs phase modulation and polarization modulation for each single photon, passes through the quantum channel, and enters the multi-user unit Bob monopole polarization demodulation and phase demodulation. The specific modulation demodulation process is described in detail in FIGS. 2 and 3 I do not repeat anymore.

FIG. 5 is a key distribution method applying the phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system, including the following procedure.

S1. Hardware Initialization: Check the software and hardware facilities of the Alice stage and each unit Bob client stage, and check whether the equipment is operating normally, the correct operating voltage and the appropriate operating temperature.

S2. System noise measurement: The system noise level is measured under the condition that the laser pulse train is not fired at the Alice stage, that is, when the pulse train value is zero.

S3. Fiber Length Measurement and Pulse Time Delay Setting: A set of pulses is sent at the Alice stage and the length of the optical fiber in the link is determined by measuring the arrival time of a pulse at each Bob client stage, Based on the relationship between the stages, the optical fiber length of each unit Bob client end is preset, and the time delay between the upper arm path and the lower arm path of each unit Bob client end is set.

S4. Wavelength addressing: The wavelength selector selects wavelength pulses suitable for use by each client Bob terminal in accordance with the wavelength allocation scheme, assigning pulsed beams of different wavelengths to the corresponding client Bob client terminals to provide one-to- Go ahead.

S5. Key transmission: The multi-wavelength pulse generator generates a pulse whose pulse period is greater than a time delay T, attenuated to a single photon level after the attenuator, and then transmitted through the first polarization beam splitter to the upper arm path Enters the lower arm path and forms two pulses with a time delay of T. After reaching the first beam combiner, they are combined and then the phase modulator, the first polarization modulator and the second polarization modulator are sequentially passed, Is transmitted in the same polarization state, and finally the polarization unit and the phase demodulation are performed after the unit Bob client ends.

S6. Key Filtering and Coding: Each unit Bob client side records the detector response. And wherein the first photon detectors, the second photon detectors, the third photon detectors, and the fourth photon detectors respond to the first photon detectors, the second photon detectors, the third photon detectors, and the fourth photon detectors The Alice terminal forwards the response time to the Alice terminal, and the Alice terminal forwards the corresponding key string based on the data transmitted from each unit Bob client terminal, and discards the other key string.

Each unit Bob shares the client-side key.

If the security key priority is Bobi> Bobj, Bobj shares Bobi's key, Alice is the intermediate node, first encrypts Alice's and Bobi's keys using Alice's and Bobj's keys, Bobj sends the key to Bobj, decrypts it, gets Bobi's key, and shares the key with Bobi.

Each unit Bob's client-to-server key sharing is exclusive. The key of any one unit Bob client can only be shared with one unit Bob client unit, and can not be shared with another unit Bob client unit after sharing.

The phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system and the key distribution method used in the present invention can realize one-to-many quantum key sharing, effectively expand the information transmission capacity, And other QKD schemes.

The present invention utilizes a phase and polarization unified modulation method that transmits two bits of information to one photon and improves the photon utilization from 0.5 to 2 originally. Compared to the existing scheme, this scheme reduces the use of components, Simplifies the structure, and improves the continuity, validity and key generation rate of information.

The present invention utilizes four electron detectors to measure atmospheric in eight timeslots in each time of communication, which results in a failure rate of 33.3% due to the dark count of the detector as compared to the atmospheric measurement in twelve time slots in each communication of the existing scheme, So that the system is more efficient and stable. The present invention utilizes a typical DPS quantum key distribution scheme in which each phase difference is in one phase encoding through the phase difference of the bifurcated interference pulse with an encoding interval of T (i.e., time delay T and T is picosecond) And sequence attacks, effectively reducing the efficiency of the eavesdropper Eve.

The positional relationship in the drawings is used for illustrating the embodiment, and should not be construed as limiting the present invention.

It should be apparent that the above-described embodiments of the present invention are provided to more fully describe the present invention and are not intended to limit the manner in which the present invention may be practiced. Those skilled in the art will appreciate that various modifications and changes may be made without departing from the spirit and scope of the present invention. There is no need to enumerate all implementations, nor can it. All changes, substitutions and improvements that come within the spirit and scope of the present invention should be included within the scope of the claims of the present invention.

101: Common optical fiber 102: Wavelength router device-102
103, 104, 105: dedicated optical fiber 201: multi-wavelength laser device
202: attenuator 203: first polarizing beam splitter
204: first beam combiner 205: phase modulator
206: first polarization controller 207: second polarization controller
301: second polarizing beam splitter 302: third polarization controller
303: Third polarized beam splitter 304: Second beam combiner
305: first photon detector 306: second photon detector
307: Fourth polarization controller 308: Fourth polarization beam splitter
309: Third beam combiner 310: Third photon detector
311: Fourth photon detector

Claims (10)

An Alice control stage comprising a multi-wavelength laser generator, an attenuator, a first polarization beam splitter, a first beam combiner, a phase modulator, a first polarization controller and a second polarization controller;
A wavelength division multiplexing unit including a wavelength selection device; And
A multi-user Bob stage, and an Alice stage is a phase-polarized multi-degree-of-freedom modulated quantum key distribution (QKD) network system connected to a multi-user Bob stage through the wavelength division multiplexing unit,
Wherein the multi-user Bob stage comprises a plurality of unit Bob client stages receiving different frequency bands, each unit Bob client stage comprising a second polarization beam splitter, a third polarization controller, a fourth polarization controller, a third polarization beam splitter , A fourth polarization beam splitter, a second beam combiner, a third beam combiner, a first photon detector, a second photon detector, a third photon detector, and a fourth photon detector,
Wherein the multi-wavelength laser generator generates a pulse train having a plurality of wavelengths and is then attenuated by the attenuator into a single photon pulse, wherein the single photon pulse is split into a vertical polarized pulse and a horizontal polarized pulse by the first polarized beam splitter The vertical and horizontal polarized pulses pass through an upper arm path and a lower arm path, respectively, and then enter the first beam combiner and are then combined. k = 0, 1) phase to reach the first polarization controller and the second polarization controller, respectively, to proceed with the polarization rotation of the pulse, and finally the two pulses enter the multi-user Bob stage with the same polarization state,
When a multi-wavelength laser pulse of the same polarization is transmitted to the wavelength router apparatus, the unit Bob client end of the corresponding wavelength is selected in an addressing manner according to wavelength, and the polarization demodulation is performed by the second polarization beam splitter of the unit Bob client end, And a horizontal polarization pulse is selected to pass through the third polarization controller when the polarization bit is " 0 ", and a vertical polarization pulse is selected to pass through the fourth polarization controller when the polarization bit is " And,
A pulse is output from the third polarization controller and passes through the third polarization beam splitter, and then an upper arm path and a lower arm path are formed. In the upper arm path, a prepulse passes through the second polarizer And the lower arm path is a path in which a back pulse (afterpulse) arrives at the second beam combiner, and the two light beams of the upper arm path and the lower arm path are transmitted to the second beam com Generating interference in the binarizer, then the first photon detector and the second photon detector make an identification response based on the randomly modulated phase difference,
After passing through the fourth polarization beam splitter output from the fourth polarization controller, two paths of an upper arm path and a lower arm path are formed, and the upper arm path is connected to the third beam combiner And the lower arm path is a path in which the rear pulse arrives at the third beam combiner, and the two light beams of the upper arm path and the lower arm path cause interference in the third beam combiner, And the third photon detector and the fourth photon detector identify and respond based on the randomly modulated phase difference. ≪ Desc / Clms Page number 13 > The system of claim 1, wherein the upper arm path further has a time delay of one T over the lower arm path. The apparatus of claim 1, wherein the first polarization controller

Polarized light and the second polarization controller rotates the pulse

(QKD) network system according to claim 1, wherein the values of n are respectively " 0 " or " 1 ". The system of claim 1, wherein the wavelength router device is a wavelength division multiplexer, an arrayed waveguide grating, a Bragg grating or a wavelength selective switch. 2. The multi-wavelength pulse laser device of claim 1, wherein the multi-wavelength laser generator comprises a multi-wavelength pulse laser device and a wavelength selector, the multi-wavelength pulse laser device comprising an interfering multi- Phase modulated quantum key distribution (QKD), characterized in that a pulse laser is generated and then selected by the wavelength selector so that each unit Bob client end can select a pulsed laser of a corresponding wavelength. Network system. 6. The system of claim 5, wherein the wavelength is selected using the wavelength selective second order equal frequency spacing scheme. 3. The apparatus of claim 1, wherein the first photon detector, the second photon detector, the third photon detector, and the fourth photon detector respond based on the phase difference of the pulses, and when the phase difference of two consecutive pulses is zero, 1 detector responds and the measurement result is " 00 ", the second detector responds and the measurement result is " 01 ", and if the phase difference of two consecutive pulses is pi, the third detector responds and the measurement result is & 10 ", the fourth detector responds and the measurement result is " 11 ". < / RTI > 2. The system of claim 1, wherein the unit Bob client end is Bobn and n is a non-zero natural number. Hardware initialization step (S1) to check the software and hardware facilities of the Alice stage and each unit Bob client stage, and check whether the equipment is operating normally, and whether the correct operating voltage and proper operating temperature are set.
(S2): a system for measuring the system noise level when the pulse string value of the premise that does not emit a laser pulse string at the Alice stage is 0;
The length of the optical fiber in the link is determined by measuring the time at which the pulse arrives at each unit Bob client end, and the length of the optical fiber in each link Bob Setting a fiber length of the client end in advance and setting a time delay between the upper arm path and the lower arm path of each unit Bob client end;
The wavelength selection apparatus selects wavelength pulses suitable for use by each unit Bob client unit in accordance with the wavelength distribution plan and assigns the pulse light beams of different wavelengths to the corresponding unit Bob client unit to perform wavelength- Step S4:
The multi-wavelength pulse generator generates a pulse, the pulse period is greater than the time delay T, attenuated to a single photon level by the attenuator, then enters the upper arm path and the lower arm path through the first polarization beam splitter, After two pulses with a delay of T are formed and combined to arrive at a first beam combiner, the pulses are then sequentially phase modulated and polarized by the phase modulator, the first polarization modulator and the second polarization modulator, A key transmission step (S5) in which polarization is demodulated and phase demodulated by each unit Bob client terminal,
A response time of each of the first photon detector, the second photon detector, the third photon detector and the fourth photon detector is recorded by each unit Bob client terminal and the response time of the first photon detector, the second photon detector, the third photon detector And a response time of the fourth photon detector to the Alice terminal, wherein the Alice terminal is configured to perform key filtering and key filtering to hold a corresponding key string based on data transmitted from each unit Bob client terminal, And a coding step (S6). ≪ RTI ID = 0.0 > (Q6D) < / RTI & The method of claim 9, characterized by key sharing between each unit Bob client end,
If the security key priority is Bobi> Bobj, Bobj shares Bobi's key, and Alice is the intermediate node, first encrypting Alice's and Bobi's keys using keys of Alice and Bobj, Bobj sends the code to Bobj, decrypts it, gets Bobi's key, shares the key with Bobi,
The key sharing between each unit Bob client end is exclusive so that the key of one unit Bob client end can be shared only with one unit Bob client end and the phase that can not be shared with another unit Bob client end after sharing Polarization multi - degree of freedom modulated quantum key distribution (QKD) method.

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